Lower Seizure Freedom Rates With Minimally Invasive Epilepsy Procedures Than Traditional Surgeries

Konstantin Kohlhase, MD

The results of a newly published systematic review of a number of databases have identified a number of possible advantages and comparisons between minimally invasive and traditional surgical approaches to treating mesial temporal lobe epilepsy (mTLE).

Particularly, the data suggest that magnetic resonance‐guided laser interstitial thermal therapy (MRgLITT) is safe and effective but has a significantly lower rate of Engel Class I outcomes, defined as seizure freedom, compared to the conventional approaches of anterior temporal lobe resection (ATL) or selective amygdalohippocampectomy (sAHE). Similar rates of Engel Class I outcomes were observed with radiofrequency ablation (RFA), though MRgLITT and RFA showed a tendency to be more advantageous compared to ATL and sAHE in terms of procedure complications.

Additionally, it appears possible for cognitive function to be affected by all of the mentioned procedures, but lateral temporal functions such as naming or object recognition were less affected by MRgLITT.

The authors, including Konstantin Kohlhase, MD, center of neurology and neurosurgery, University Hospital Frankfurt, noted that long-term data are available for outcomes after ATL, showing seizure freedom in just over 40% of patients after 10 years and just over 35% of patients after 15 years, but no such data are available on MRgLITT.

“However, because the tissue is not completely removed in comparison with open surgery, insufficient destruction can lead to reorganization of epileptic networks and, thus, to a recurrence of seizures, which emphasizes the importance of good patient and surgical technique selection,” Kohlhase et al. wrote. “Whereas data on conventional epilepsy surgery suggests that outcome after 1 year is already a good predictor for long‐term seizure outcome, comparably robust data after MRgLITT or RFA is not yet available.”

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The review included 43 studies (13 MRgLITT, 6 RFA, and 24 surgery studies) involving 554, 123, 1504, and 1326 patients treated by MRgLITT, RFA, ATL, or sAHE, respectively. Data were compiled from MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews.

Ultimately, Engel Class I outcomes were achieved at ≥6-month follow up each procedure as follows: MRgLITT: 57% (n = 315; range, 33.3-67.4); RFA: 44% (n = 54; range, 0-67.2); ATL: 69% (n = 1032; range, 40-92.9); sAHE: 66% (n = 887; range, 21.4–93.3) (FIGURE).

FIGURE. Engel Class I Outcomes Post-Procedure.

There were no marked differences in seizure outcomes between the MRgLITT and RFA groups (Q = 2.74; P = .098), although both ATL and sAHE were found to be superior to MRgLITT (ATL: Q = 8.92, P = .0028; sAHE: Q = 4.33, P = .0374) and RFA (ATL: Q = 6.42, P = .0113; sAHE: Q = 5.04, P = .0247).

Better outcomes were reported in patients with follow‐up of 60 months or more—a subgroup analysis carried out due to the large variance in follow-up in the surgery group. The follow‐up period among patients treated by MRgLITT ranged from 6 to 70 months, while the follow‐up period in the RFA group ranged from 12 to 62 months. The follow‐up period after ATL was 36.3 months (±29.0; range, 12-116.4) and after sAHE was 36.4 months (±25.6; range, 12-104.4).

In the ≥60‐month group, mean Engel Class I outcome was 72.7% after ATL (474 of 652; range, 46.3-89.3) and 68.5% after sAHE (376 of 549; range, 44.4-81.5). Those mean rates in the <60-month follow-up group for ATL and sAHE were 65.5% (558 of 852; range, 40-92.9) and 65.8% (511 of 777; range, 21.4-93.3), respectively. Subgroup analysis revealed a significantly better Engel Class I outcome between ATL (≥60 months) and MRgLITT (Q = 6.68; P = .009) or RFA (Q = 7.4; P = .006), respectively. As well, sAHE (≥60 months) resulted in a significantly higher rate of Engel Class I outcome compared to MRgLITT (Q = 4.09; P = .043) or RFA (Q = 5.8; P = .016).

“For the selection of patients, mesial [hippocampal sclerosis] might be a prognostic factor for a more favorable outcome in patients treated by MRgLITT,” Kohlhase and colleagues wrote. They added that “the high heterogeneity in RFA suggests that some approaches such as the occipital approach may be similar to MRgLITT, whereas others are not.”

The rate of Engel Class I outcome in patients with mTLE and hippocampal sclerosis (HS) treated by MRgLITT was 64% (123 of 192), with meta‐analysis comparison with non‐mTLE and HS patients showing significantly better outcomes in those with proven mTLE and HS (Q = 8.55; P = .0035).

The rates of overall complications were 14.1% (37 of 262), 17.5% (19 of 108), 31.3% (72 of 230), and 18.2% (27 of 148) for MRgLITT, RFA, ATL, and sAHE, respectively. Major complications occurred at respective rates of 3.8% (n = 10) for MRgLITT, 3.7% (n = 4) for RFA, 10.9% (n = 25) for ATL, and 7.4% (n = 11) for sAHE, with no statistically significant differences.

Neuropsychological deficits occurred after all procedures, with left‐sided surgeries showing a higher rate of verbal memory impairment. Although lateral functions such as naming or object recognition might be preserved in MRgLITT, the group noted.

“Between MRgLITT and RFA there were no significant differences in Engel‐I outcome, whereby the success of treatment seems to depend on the approach used (e.g., occipital approach),” wrote Kohlhase and colleagues. “MRgLITT shows a similar rate of complications compared to RFA, whereas patients undergoing MRgLITT may experience fewer major complications compared to ATL or sAHE and might have a more beneficial neuropsychological outcome.”

REFERENCE
Kohlhase K, Zöllner JP, Tandon N, Strzelczyk A, Rosenew F. Comparison of minimally invasive and traditional surgical approaches for refractory mesial temporal lobe epilepsy: A systematic review and meta‐analysis of outcomes. Epilepsia. Published online Mar